The present disclosure relates generally to the field of aircraft radar systems. More specifically, the application relates to a radar system for determining the ground speed or drift angle of an aircraft in a different manner depending on whether or not weather is detected.
Doppler weather radar systems for aircraft may be used for wind shear detection using wind shear processing based on Doppler processing on radar beam returns to determine a high gradient of wind velocities in a localized area.
Doppler processing in Doppler weather radar systems may also be used to determine aircraft ground speeds as well as aircraft drift angle based on spectral processing, where the speed of the aircraft relative to the ground is determined. The aircraft drift angle is the horizontal angle between the long axis of the aircraft and the tangent to its path. Current generation radars can detect aircraft ground speeds to within a few knots using Doppler processing.
Detecting aircraft ground speeds using Doppler processing, however, may be inaccurate especially in the presence of heavy precipitation. The weather may contaminate the radar returns resulting in the inaccuracy.
External sensors such as inertial navigation systems or GPS systems, may also determine the aircraft ground speed. If such external sensors fail, Doppler weather radar systems may be used to determine the aircraft ground speed. In this case, the failure of Doppler processing using conventional Doppler weather radar systems to accurately detect ground speeds in the presence of weather is particularly problematic.
Therefore, there is a need for an aircraft radar system and method to accurately determine aircraft ground speed as well as drift angle in the presence of weather.